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Pre-virtualization: Soft layering for virtual machines


Joshua LeVasseur, Volkmar Uhlig, Yaowei Yang, Matthew Chapman, Peter Chubb, Ben Leslie and Gernot Heiser

University of Karlsruhe

IBM Watson




Despite its current popularity, para-virtualization has an enormous cost. Its deviation from the platform architecture abandons many of the benefits of traditional virtualization: stable and well-defined platform interfaces, hypervisor neu- trality, operating system neutrality, and upgrade neutral- ity—in sum, modularity. Additionally, para-virtualization has a significant engineering cost. These limitations are accepted as inevitable for significantly better performance, and for the ability to provide virtualization-like behavior on non-virtualizable hardware such as x86.

Virtualization and its modularity solve many systems problems, and when combined with the performance of para-virtualization become even more compelling. We show how to achieve both together. We still modify the guest operating system, but according to a set of design princi- ples that avoids lock-in, which we call soft layering. Ad- ditionally, our approach is highly automated and thus re- duces the implementation and maintenance burden of para- virtualization, which is especially useful for enabling obso- leted operating systems. We demonstrate soft layering on x86 and Itanium: we can load a single Linux binary on a variety of hypervisors (and thus substitute virtual machine environments and their enhancements), while achieving es- sentially the same performance as para-virtualization with less effort.

BibTeX Entry

    publisher        = {Springer},
    author           = {LeVasseur, Joshua and Uhlig, Volkmar and Yang, Yaowei and Chapman, Matthew and Chubb, Peter and
                        Leslie, Ben and Heiser, Gernot},
    year             = {2008},
    month            = aug,
    editor           = {{Yeh-Ching Chung, John Morris}},
    title            = {Pre-virtualization: soft layering for virtual machines},
    booktitle        = {Asia-Pacific Computer Systems Architecture Conference},
    pages            = {1-9},
    address          = {Hsinchu, Taiwan}


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